Last week, I talked about the fact that, over short distances, there’s just no acoustical substitute for a good physical barrier between you and your neighbor. But what is a good physical barrier?
There are several factors to consider, depending on the type of barrier: its height, how much it reduces sound as it passes through it, any gaps between and under it, and how absorptive it is. A barrier’s performance is the sum total of these factors. You may be surprised to hear that even the direction in which an occupant faces affects their voice’s volume in the neighboring workspace.
But I think the most topical discussion concerns workstation partition height. Today, there are numerous pressures to reduce it (or eliminate workstations altogether), including initial cost savings, sustainability (i.e. for daylighting and material reduction) and the trend towards ‘collaborative’ and benching designs. Unfortunately, eliminating these barriers has a dramatic impact on the acoustical performance of the space – particularly at close quarters.
So, how high is high enough? I’ve heard a lot of different responses to this question from those involved in the world of office design, but there’s little debate within the acoustical community. For decades, the answer given by acoustical engineers, consultants and researchers has always been: above seated head height. Partitions much taller than that (say above standing line of sight) have an ever decreasing impact. Ones below seated head height don’t block voices or noise (though if they’re absorptive, they may still contribute to that requirement)...they simply hold up your desk.
Even when there’s conceptual agreement that individual workspaces should provide seated privacy with partitions ‘above seated head height,’ there’s still some disagreement as to what this means in terms of actual height. Some suggest that 48-to 51-inch (1.2 - 1.3 m) partitions meet the seated privacy requirement. But do they?
Fortunately, there are standard reference documents that tell us exactly what seated head height is. Among others, the Business and Institutional Furniture Manufacturer’s Association (BIFMA) published the BIFMA Ergonomic Guidelines in 2002. This document outlines a variety of human dimensions in a seated position, providing a range that covers up to the 95th percentile. In other words, it covers all but the 5% tallest people.
According to the BIFMA document, the sitting head height of the 95th percentile male is 58.2 inches (1.48 m). So, for a workstation partition to be ‘above seated head height,’ it must be slightly taller. Let’s also not forget that if we design for the 95th percentile, 5 out of 100 occupants will be taller still. So it’s best to design with some additional leeway to be as inclusive as possible.
This data supports what the acoustical community has said for decades: that workstation partitions must be between 60 to 65 inches in height (1.5 - 1.65 m) in order to be above seated head height and provide acoustical isolation.
This answer might not appeal to the aesthetic sensibilities of some readers. However, it all comes down to the behavior of sound and the reality of how tall people are...and the fact that they need to be able to concentrate on their tasks when in the workplace.